Association Of Dietary Fat Intake Research Articles

Bridging animal and human studies: what are the missing segments in dietary fat and prostate cancer?

Epidemiologic investigations have suggested an association of dietary fat intake with prostate cancer risk, especially risk of advanced prostate cancer. However, supporting evidence from animal studies is limited. Segments that would bridge animal and human studies on dietary fat and prostate cancer--which would determine the future directions of research--are missing. Such segments include 1) well-designed animal studies to evaluate whether dietary fat or fatty acid modulation, particularly by reducing dietary fat and supplementing n-3 fatty acids, reduces the progression of prostate cancer; 2) in vivo identification of intermediate biomarkers that are responsive to dietary fat and fatty acid treatment and may serve as surrogate endpoints in future clinical studies; 3) elucidation of mechanisms by which dietary fat or fatty acid modulation could prevent prostate cancer progression; 4) further epidemiologic studies to estimate dietary exposure more precisely to establish the correlation between dietary fat and risk of prostate cancer; 5) randomized clinical intervention trials evaluating whether dietary fat reduction combined with dietary n-3 fatty acid supplementation delays the recurrence of prostate cancer and improves survival in patients with clinical disease after therapeutic treatment, and whether it prevents or reduces the progression to clinically significant disease in men with latent disease; and 6) studies validating intermediate biomarkers as surrogate endpoints.

Dietary Lipid Intake and Serum Lipids in Older Men and Women: A Longitudinal Study.

The relationship of dietary fat to atherosclerosis is an area of continuing research. In order to establish if there is a seasonal variation in lipid status, we determined the dietary intake of lipids as well as their serum levels in 65 (33 males and 32 females) free-living subjects (67-75 years) in winter and summer. Both fat and cholesterol intakes were generally higher for men than women, but no seasonal differences were found for either gender. Nor in either sex was there any significant association of dietary fat intake (polyunsaturated/saturated fatty acid ratio) with either triglycerides or cholesterol levels in serum. Dietary unsaturated fatty acid but not the cholesterol intake appeared to have a marginal effect on serum cholesterol. According to the Canadian Society of Clinical Chemists reference standards for total serum cholesterol, 18% of the men and 41% of the women in this study population would be classified as high-risk (>5.2mmol/liter). HDL cholesterol, however, was consistently higher in the women. Total fat intake contributed 34% of total energy for both genders regardless of the season.

Usual dietary fat intake and insulin concentrations in healthy women twins.

To evaluate the associations between the usual intake of dietary fats and insulin concentrations. Insulin concentrations and insulin resistance have been positively related to risk for NIDDM, obesity, hypertension, dyslipidemia, and coronary heart disease, yet little is known of the environmental risk factors for relative hyperinsulinemia. Insulin resistance can be induced by high-fat feeding in laboratory animals; therefore, high-fat diets may increase risks for developing NIDDM. Subjects included 544 nondiabetic women who participated in the second examination of the Kaiser Permanente Women Twins Study (1989-1990). Fasting and 2-h post 75-g glucose load insulin levels were determined. Dietary fat intake was assessed by a food frequency questionnaire. Generalized least-squares regression analyses for unpaired twin data were used to determine the relationship between dietary fat intake and insulin levels after adjustment for total calories, age, several behavioral variables, and in some models, percentage of body fat and waist-to-hip ratio. Associations of dietary fat intake with insulin levels were also evaluated within the subset of monozygotic twin pairs (n = 164 pairs) after removal of genetic influences by regression analysis of intrapair differences. Among the 544 individual women, a 20 g/day increase in total dietary fat was associated with a higher fasting insulin level (9% [P < 0.001] before and 6% [P < 0.01] after adjustment for the obesity variables). Higher intakes of saturated fat, oleic acid, and linoleic acid were each positively related to higher fasting insulin values. The relation of dietary fat with fasting insulin was significantly attenuated among physically active women compared with those who were sedentary (P = 0.04), even after adjustment for obesity. Only saturated fat intake was significantly associated with 2-h postglucose load insulin level before (P = 0.004) but not after adjustment for obesity. Within identical twin pairs, total dietary fat was positively related to fasting insulin before (P = 0.03) but not after adjustment for obesity (P = 0.11). High intake of total dietary fat is positively related to relative fasting hyperinsulinemia in nondiabetic women, particularly those who are sedentary. This effect appears to be partly mediated by the relation of dietary fat with obesity.